"I don't really understand why we have to keep such an agreement closed," Putin was quoted as saying Saturday during a trip to Kyrgyzstan.

He suggested Washington's resistance stems from a hope to retain the combat potential of forces fighting the Syrian government.

"This comes from the problems the U.S. is facing on the Syrian track — they still cannot separate the so-called healthy part of the opposition from the half-criminal and terrorist elements," he said. "In my opinion, this comes from the desire to keep the combat potential in fighting the legitimate government of Bashar Assad. But this is a very dangerous route."